1. Field of the Invention
The present invention relates generally to slide fasteners, and more particularly to stringer tapes for slide fasteners suitable for use with sporting goods, bags, athletic apparel and the like which require the slide fastener to be stretchable, particularly transversely thereof.
2. Prior Art
British Pat. No. 1,396,577 discloses a pair of first and second types of transversely stretchable stringer tapes for slide fasteners. The first type of stringer tape has a transversely stretchable portion in which each of a set of only elastic weft yarns extends across two or three adjacent wales. Such a string tape tends to be unnecessarily stretched when a slider is moved along the slide fastener for opening and closing it and this stretching often causes the stringer tape to become wavy or puckered, and further, the set of only elastic weft yarns can be easily broken or otherwise damaged. With the prior stringer tape, therefore, a smooth and proper opening and closing operation of the slide fastener is difficult to achieve.
In the second type of stringer tape, a stretchable portion has a warp-knit ground structure composed of chain stitches and tricot stitches, both formed of non-elastic yarns. A set of laid-in elastic weft yarns each extend across three adjacent wales, and each of the non-elastic yarns of tricot stitches extends across an adjacent pair of wales. The non-elastic yarns are usually made of multifilament yarns that are subject to becoming shrunk and objectionably rigid when the tape is heated due to treatment such as heat-setting and dyeing. Consequently, the second type of stringer tape has only a fairly limited degree of stretchability.